During fabrication of the body structure of a motor vehicle (referred to as the body-in-white), a multitude of panels and braces are attached to a floor structure (or floor pan) assembly. The floor structure forms the base on which the body structure is assembled. Typical techniques for attaching the panels to the floor structure include welding, bonding and mechanical fasteners (such as threaded fasteners or rivets). As the floor structure moves down the assembly line, held in place by clamping fixtures, the body structure of the vehicle is assembled. This fabrication process is commonly partially or completely automated, for example utilising of robotic arms located at a series of stations along the assembly line to perform programmed tasks as the body structure travels along the line. The robotic arms are fitted with one or more tools for performing the requisite tasks at each station. The assembly process lends itself to the use of robotic arms because articulating arms can easily introduce various component braces and panels to the floor structure and perform a high number of operations in a short time frame and with a high degree of accuracy.
There are various stages in the production process where panels must be accurately aligned and joined to each other. For example, when the left and right side panels are located in relation to the floor structure and then secured in place, for example by welding or riveting. In order to ensure accurate assembly, the panels must be precisely located before they are joined. This can be accomplished using a sacrificial element which defines a reference (datum) point for locating the panel. The sacrificial element can, for example, take the form of a sacrificial strap extending across a corner of an aperture formed in the side body panel, or a sacrificial tab extending along an edge of an aperture. The sacrificial element is typically formed integrally with the panel and can comprise an alignment aperture which defines the datum point. Once the panel has been aligned, the panel can be fixed in place, for example to the floor structure and roof, by welding or riveting. The sacrificial element is subsequently removed from the panel. Typically, this has been done manually, for example using a pneumatic nibbler. However, this method of removing the sacrificial element is dependent upon the skill of an operator to ensure a satisfactory finish. The use of a pneumatic nibbler can potentially also result in the operator getting “white finger” caused by the mechanical vibration.
It is against this backdrop that the present invention has been conceived. At least in certain embodiments, aspects of the present invention seek to overcome or ameliorate problems associated with the prior art apparatus and methods.